Can someone elaborate on how Engagement works I keep getting it wrong...

An enemy is automatically engaged with an Investigator if it is ready and at the same location. This can happen by:

-you moving into its location;

-it readying in the Upkeep phase after being exhausted, say by a successful Evade attempt;

-it Spawning in your location;

-it moving into your location from the Hunter keyword, which means at the beginning of the Enemy Phase, it will move 1 location towards the nearest Investigator.

Note: Spawn is a specific keyword that tells you at which location that Enemy starts in play when revealed from the encounter deck. Absent that keyword, an Enemy will spawn engaged with the Investigator who drew it.

You may also choose to engage an Enemy not engaged with you. This is almost always from the Enemy being engaged with another Investigator, or the Enemy being Aloof - a keyword meaning it does not make automatic engagement checks.

If there is ever an option for an Enemy to potentially engage multiple Investigators (e.g. from Spawn, or from readying in Upkeep), follow the instructions of the Prey keyword, if any. If there is a tie or no Prey instructions, the lead Investigator may choose which Investigator the Enemy will engage.

Also the Speed what I gotta beat or match to escape and the stentgh is how high I gotta get to smack it?

12 minutes ago, CEOWolf said:

Also the Speed what I gotta beat or match to escape and the stentgh is how high I gotta get to smack it?

Correct. An agility test for Evade, which if successful will exhaust the Enemy; and a combat test for Fight, which if successful deals 1 base damage. The middle triangle on an Enemy's stat line is the HP.